Geothermal heating and cooling systems have become more popular for residences, new local residential community developments, industrial buildings, and other facilities in many geographic areas. They are capable of both heating and cooling, and even relatively small locations contains sufficiently large reservoirs of thermal energy. A typical suburban home may occupy a lot containing ten times the thermal energy required for an entire heating season. The energy is transferred to the facility via a heat-exchange system in a geothermal field with long sections of underground or underwater pipe containing a thermal fluid to transfer latent heat to the building during cold weather, and to transfer heat from the building to the field in hot weather. Most geothermal installations circulate a fluid such as glycol and water in a closed loop, but some may circulate locally available water in an open loop.
Fuel cells are gaining prominence as a source of electrical energy. A fuel cell is an electrochemical cell capable of converting chemical energy from a fuel and an oxidant to electricity with essentially invariant electrodes and electrolytes A number of cell types exist, and many different fuels are suitable for either direct use, or for indirect use after reforming. Although current fuel cells find applications in smaller capacities, their size, capability, and efficiency grow constantly.
Geothermal units commonly require electricity to drive the compressor, the fan, and the pump(s) that circulate their thermal fluids. Fuel cells commonly generate significant quantities of heat that is carried off by fluid-based (usually air or water) cooling systems and vented to maintain safe and efficient operating temperatures within the cells. That is, the heat generated by fuel cells is usually considered waste heat, and is disposed of without recovery. Several advantages would accrue to a composite system having coupled geothermal and fuel-cell components, if a way could be found to coordinate the stable temperature requirements of the fuel cell with the usually highly changeable and sometimes conflicting heat-transfer requirements of the geothermal system. Particular advantages may accrue to isolated buildings or other facilities, where outside electrical power may be difficult to obtain, or to facilities where returning co-generated power to a grid may be a viable option.